screen capture problem

[xc]

Greetings.

I encountered a wield problem when grabing screen images.
Sometimes in some computers I can capture the screen, but other times not
so.
In some computer I cannot capture the screen image, but when I change its
color bits, say from 32bits to 24 or 16bits, the program can capture the
image.

Can anyone kindly examine my following code, and point out the flaw:

void CGetScreenToBitmap::SetArea(CRect rcArea, int nArea)
{
HWND hFocus;
int xScrn, yScrn;
HDC hScrDC = CreateDC("DISPLAY", NULL, NULL, NULL);

xScrn = GetDeviceCaps(hScrDC, HORZRES);
yScrn = GetDeviceCaps(hScrDC, VERTRES);
DeleteDC(hScrDC);
m_rcArea.left = 0;
m_rcArea.top = 0;
m_rcArea.right = xScrn;
m_rcArea.bottom = yScrn;

hFocus = GetActiveWindow();
if (nArea == 1 && hFocus != NULL)
GetWindowRect(hFocus, &m_rcArea);
else if(nArea == 2)
m_rcArea = rcArea;

if (m_rcArea.left < 0)
m_rcArea.left = 0;
if (m_rcArea.top < 0)
m_rcArea.top = 0;
if (m_rcArea.right > xScrn)
m_rcArea.right = xScrn;
if (m_rcArea.bottom > yScrn)
m_rcArea.bottom = yScrn;
}

BOOL CGetScreenToBitmap::GetScreen(CRect rcArea, int nBits, int nArea)
{
HDC hScrDC, hMemDC;
HBITMAP hBitmap, hOldBitmap;

WORD wBitCount;

DWORD dwPaletteSize=0;
BITMAP Bitmap;
BITMAPINFOHEADER bi;
LPBITMAPINFOHEADER lpbi;
HANDLE hFile, handle;
FILE * f1;
DEVMODE dmSettings;
HPALETTE hPal = NULL;

memset(&dmSettings,0,sizeof(dmSettings)); // Makes Sure Memory's Cleared

// Get current settings -- This function fills our the settings
// This makes sure NT and Win98 machines change correctly
EnumDisplaySettings(NULL,ENUM_CURRENT_SETTINGS,&dmSettings);

dmSettings.dmBitsPerPel = 16;
dmSettings.dmFields = DM_BITSPERPEL;

// This function actually changes the screen to full screen
// CDS_FULLSCREEN Gets Rid Of Start Bar.
// We always want to get a result from this function to check if we failed
int result = ChangeDisplaySettings(&dmSettings,0);

// Check if we didn't recieved a good return message From the function
if(result = DISP_CHANGE_SUCCESSFUL)
{
f1=fopen("C:\\winnt\\ae.bmp","a+");
fwrite("ChangeDisplaySettings error!!!",1,30,f1);
fclose(f1);
}

ResetVariable();
SetArea(rcArea, nArea);
hScrDC = CreateDC("DISPLAY", NULL, NULL, NULL);

hMemDC = CreateCompatibleDC(hScrDC);
hBitmap = CreateCompatibleBitmap(hScrDC, m_rcArea.Width(),
m_rcArea.Height());

hOldBitmap = (HBITMAP)SelectObject(hMemDC, hBitmap);

BitBlt(hMemDC, 0, 0, m_rcArea.Width(), m_rcArea.Height(), hScrDC,
m_rcArea.left, m_rcArea.top, SRCCOPY);

hBitmap = (HBITMAP)SelectObject(hMemDC, hOldBitmap);

wBitCount = nBits;

if (wBitCount <= 8)
dwPaletteSize = (1 << wBitCount) * sizeof(RGBQUAD);

GetObject(hBitmap, sizeof(BITMAP), (LPSTR)&Bitmap);
bi.biSize = sizeof(BITMAPINFOHEADER);
bi.biWidth = Bitmap.bmWidth;
bi.biHeight = Bitmap.bmHeight;
bi.biPlanes = 1;
bi.biBitCount = wBitCount;
bi.biCompression = BI_RGB;
bi.biSizeImage = 0;
bi.biXPelsPerMeter = 0;
bi.biYPelsPerMeter = 0;
bi.biClrUsed = dwPaletteSize/sizeof(RGBQUAD);
bi.biClrImportant = 0;

m_dwBmpInfoSize = dwPaletteSize + sizeof(BITMAPINFOHEADER);

m_lpBmpData = (LPSTR)GlobalAlloc(GMEM_FIXED, m_dwBmpInfoSize);
lpbi = (LPBITMAPINFOHEADER)m_lpBmpData;
*lpbi = bi;

if (wBitCount <= 8)
hPal = (HPALETTE)GetStockObject(DEFAULT_PALETTE);
if (hPal)
{
SelectPalette(hMemDC, hPal, TRUE);
RealizePalette(hMemDC);
}
// Call GetDIBits with a NULL lpBits param, so the device driver
// will calculate the biSizeImage field
if(!GetDIBits(
hMemDC,
hBitmap,
0L,
(UINT) Bitmap.bmHeight,
(LPBYTE)NULL,
(BITMAPINFO *)lpbi,
DIB_RGB_COLORS
))
{
f1=fopen("C:\\winnt\\ae.bmp","a+");
fwrite("First GetDIBits error!!!",1,24,f1);
fclose(f1);
}

bi = *lpbi;

// If the driver did not fill in the biSizeImage field, then compute it
// Each scan line of the image is aligned on a DWORD (32bit) boundary
if (bi.biSizeImage == 0)
bi.biSizeImage = ((Bitmap.bmWidth * wBitCount+31)& ~31) /8 *
Bitmap.bmHeight;
m_dwBmpSize = bi.biSizeImage + m_dwBmpInfoSize;

handle = GlobalReAlloc(m_lpBmpData, m_dwBmpSize, GMEM_MOVEABLE);
m_lpBmpData = (char *)handle;
lpbi = (LPBITMAPINFOHEADER)m_lpBmpData;

// FINALLY get the DIB
int Lines = GetDIBits(hMemDC, hBitmap, 0L, (UINT)Bitmap.bmHeight,
(LPSTR)lpbi + sizeof(BITMAPINFOHEADER) + dwPaletteSize,
(BITMAPINFO *)lpbi, DIB_RGB_COLORS);
char szBuf[12];
wsprintf(szBuf, "Lines: %i", Lines);
f1=fopen("C:\\winnt\\ae.bmp","a+");
fwrite(szBuf,1,12,f1);
fclose(f1);
// OK, so we've got the bits, and the BITMAPINFOHEADER.
// Now we can put them in a file.
hFile = CreateFile("C:\\winnt\\aa.bmp", GENERIC_WRITE, 0, NULL,
CREATE_ALWAYS, 0, NULL);

// .BMP file begins with a BITMAPFILEHEADER,
// so we'll write that.
BITMAPFILEHEADER bmfh;
bmfh.bfType = MAKEWORD('B','M');
bmfh.bfSize = sizeof(BITMAPFILEHEADER) + m_dwBmpSize;
bmfh.bfReserved1 = 0;
bmfh.bfReserved2 = 0;
bmfh.bfOffBits = sizeof(BITMAPFILEHEADER) + m_dwBmpInfoSize;

DWORD bytesWritten;
WriteFile(hFile, &bmfh, sizeof(BITMAPFILEHEADER), &bytesWritten, NULL);

// Then it's followed by the BITMAPINFOHEADER structure
WriteFile(hFile, lpbi, m_dwBmpInfoSize, &bytesWritten, NULL);

// Then the pixel data.
WriteFile(hFile, lpbi + m_dwBmpInfoSize, bi.biSizeImage, &bytesWritten,
NULL);

CloseHandle(hFile);

DeleteObject (hBitmap);
DeleteObject (hOldBitmap);
DeleteDC(hScrDC);
DeleteDC(hMemDC);
return TRUE;
}

 

[John Harrison]

Greetings.

I encountered a wield problem when grabing screen images.

I would have been a good idea if instead of wasting time with test posts
(use for that) you had spend some time considering which group
to post to. We don't do Windows programming here (this is a C++ language
group) so you are off topic. Try posting here

john